The purpose of this program project is to learn the causes of aging as they apply to the nervous system. To accomplish this goal investigators from the disciplines of biochemistry, anatomy and psychology have come together to carry out a multidisciplinary study. This includes behavioral and anatomical aspects of audition, aging changes in the cerebral cortex, the olfactory system, and the hippocampus, and the effects of aging on the microvessels of the brain, and upon the chromatin of neuronal and neuroglial cells. In addition, we intend to initiate a study of the effects of restricted diet on the lifespan span of rats. Interrelations exist between the eight projects included in this application, so that some of the aspects of aging being considered include normal aging changes, plasticity and aging, transneuronal degeneration, and senile plaques.